Omc 120 3000 Rpm At Full Load?

[powerabout]

A Mercruiser 120 which is the 153cu in chev like yours has a full throttle operating range of 3900-4300
So you want over 4000 with a lightly loaded boat.

Did you look at the mechanical advance in the distributor as Frosty mentioned?
We need to know the sterndrive gear ratio to determine how the 15" prop will perform.
I would guess a 15 prop on that boat would get it over 4000rpm depending on the drive ratio..

Sorry..that engine photo is not yours is it?
Can you post one

 

[stanl]

hello powerabout,the motor runs pretty good for bein such an girl,oil pressure is never below45 and 55-60 at 3000 rpm, my concern is overeving.in addition to this WOT question, why is it i cannot find a SEASWIRL home page or archives that give info on thier product?i live here in PORTLAND,OREGON and from what i can figure ,they are built right over MT, HOOD in madras,ore. ENGINE MODEL#990242D,,,, OUTDRIVE MODEL#981110, SERIAL#W153435,,again thanks for the help,,,,,,,,stanl 4000rpm wow

 

[stanl]

stanl here,here are some pics of my 1978 seaswirl,you mention MERCRUISER in last reply ,,i thought was a ford product,i know nothing,but i do know i have a chev. thankyou again for your replys,i am learning everyday.,,,,,,,,stanl

 

[stanl]

stanl here again, with more pics. is the engine that was nicknamed "the iron duke"??? must be fun scootin in and around three different countrys,what do you do?,,,,,,stanl

 

[powerabout]

The package will last for years as long as you flush out the sea water after use and the stern drive is full of oil.
The engine is OK to run at 4500rpm all day.
Re the performance issue have you
1. used a timing light to see if the mechanical advance is working
2. remove the flame arrestor and open the throttle fully to see that the butterflys are vertical, i.e. fully open
3. make sure the choke is coming off when the engine has warmed up
cheers

 

[Wassman]

Mechanic advance is unlikely to be not working on a new distributor. There should be no vacuum advance on a marine engine.

If your concerned about it strobe it.

How old is the fuel? I take you have never seen this motor run 5000 loaded?

Hi, I had same problem, changed prop to 14/11 now get full rpm and zero lag out of hole. Top speed 45kph at 5000 Rpm

 

[powerabout]

Hi, I had same problem, changed prop to 14/11 now get full rpm and zero lag out of hole. Top speed 45kph at 5000 Rpm

Unless that boat is very heavy it should be going faster then that, 5000 is a bit too much when going that slow